TNF and lichen planus: Studies concerning oral diseases, such as periodontal diseases, lichen planus or oral carcinoma, demonstrated the increased salivary levels of selected pro-inflammatory nuclear factor-κB dependent cytokines, e.g., interleukin 1β (IL-1β), interleukin 6 (IL-6), tumour necrosis factor α (TNF-α) [44,45,46].